Approximately 1,000 persons who underwent bionutritional and medical tests (including radiographs of the hand and os calcis for x-ray bone mineral quantitation) will be retested after a 20-25 year time lapse. Changes in individual bone mineral content and cortical volume during the intervening quarter century will be determined by radiographic densitometry using the Texas Woman's University method (with recently incorporated improved technology); direct radiographic scaling of bone morphology; and, terminally, by gamma ray absorptiometry using the Norland-Cameron method. Bone changes during the time period will be compared with the "normal" profile of bone development/regression currently being ascertained through our contractual work with the National Center for Health Statistics. This work encompasses bone mineral and cortical thickness measurements of 12,000 individuals who have been computer-selected by the Bureaus of Census to represent the United States population. The specific aim of the proposed program is to determine if bone rarefaction with age is uniform and universal, or if nutritional, environmental/occupational, or pathologic factors are conducive to deviations from the normal profile which may result in the syndrome known as osteoporosis.